ANTHOZOA—TETRACORALLA. 



57 



Found in the Onondaga limestone of New York, Canada, Mich- 

 igan, Ohio. Abundant at the Falls of the Ohio. 



7. Z. prolifica Billings. (Fig. 81.) Middle Devonic. 



Conical and generally curved, expanding rapidly. Septa meet 

 at the center of the deep calyx, where they unite more or less. 

 Broad fossula formed by abortion of cardinal septum. 



Fig. 81. Zaphrentis prolifica, lateral (a) and calicinal (b) views (after Billings). 



Found in the Onondaga limestone of Michigan, Canada, Ohio, 

 Kentucky, etc., and in the Hamilton group of Michigan, Canada, 

 etc. 



8. Z. convoluta Hall. Middle Devonic. 



Conical and rapidly expanding. The septa unite before reach- 

 ing the center and become more or less twisting. 



In the Onondaga limestones of the Falls of 

 the Ohio. 



9. Z. simplex Hall. (Fig. 82.) 



Middle Devonic. 



More cylindrical than the preceding, regu- 

 larly tapering, septa scarcely reach the center. 

 In the Hamilton shales of New York. 



10. Z. stokesi E. & H. Siluric. 

 Conical and curved with moderately deep 



calyx, in which the septa unite in the center 

 and become twisted as in Streptelasma. A 

 stong fossula and tabulae are present. 



In the Niagara of Canada, Michigan, Iowa, etc., and in equiva- 

 lent beds of Anticosti aud Lake Temiscaming. 



Fig. 82. Zaphrentis 

 simplex (Pal. N. Y., 

 Hall). 



